Vol 54, No 4 (2018)

Oxidation of paraffinic tar in two stages at different temperatures is proposed for regulating the physicochemical properties of the oxidized bitumens. The oxidation temperature is shown to be one of the decisive factors in forming an oxidized bitumen product with a hydrocarbon group composition that conforms to state standard requirements. The adhesion indicator, thermal oxidative properties, and cohesive strength of the bitumens can be improved by adjusting the first- and second-stage oxidation temperatures. The dependence between the adhesion indicator and maximal tensile strength is used for a preliminary estimate of the adhesive properties of oxidized bitumens produced by two-stage oxidation of the studied feedstock.

Dynamic adsorption parameters of CH₄, CO, CO₂ and N₂ gas mixtures on a fixed bed of Ai-Dag (Azerbaijan) natural clinoptilolite were identified. The effects of adsorbate concentration on the effective diffusion coefficient and overall mass-transfer coefficient were determined. Also, the change of clinoptilolite activity with time during CO₂ adsorption was studied. A system of equations describing the changes of effective diffusion and mass-transfer coefficients as functions of time was proposed and could be used to design the best industrial adsorbers under unsteady process conditions.

A kinetic model that covers the key reactions for alkylation catalyzed by zeolites is presented. It represents a system of ordinary first-order differential equations and forms the basis of successive construction of a computer modelling system. During investigation of the alkylation of isobutane by olefins a scheme was compiled for the conversion of hydrocarbons, and differential equations describing the rates of the chemical reactions involved in the alkylation of isobutane by olefins were formulated. The kinematic parameters of the reactions were determined by seeking the reaction rate constants in a solution of the reverse kinematic problem. The initial data for solving the inverse kinetic problem are also the technological mode of operation of the pilot plant and the composition of the products of the alkylation process. A set of differential equations was formulated in order to solve the computer model under the initial conditions of the alkylation process for the overall chemical reactions of each group of substances without taking account of some of the intermediate reactions. The system of differential equations was solved by the Euler method with the subsequent production of a better set of reaction rate constants for each record in the experimental data.

A study was carried out on the effect of ionic liquids (morpholine formate and aniline formate) on the desulfurization of catalytic cracking gasoline and coking gasoline. A relationship was found between the extent of desulfurization of the gasolines on the ionic liquid:gasoline ratio and the duration of the extraction. An increase in the ionic liquid: coking gasoline ratio from 1:10, to 1:5, and then 1:1 led to enhancement of desulfurization t o 19.5%, 21.5%, and 49%, respectively. An increase in the ionic liquid: catalytic cracking gasoline ratio from 1:3 to 1:1 led to an increase in the desulfurization of this gasoline from 40.2% to 65.4% for 0.2 h extraction time. When the extraction time was extended to 0.5 h, the desulfurization of catalytic cracking gasoline was enhanced from 50 to 70%.

The influence of various media on the degree of transformation of kerogen of Domanikovian rocks in hydrothermal processes was studied in model experiments. Autoclave experiments were conducted with debituminized rock in inert, hydrogen, and carbon dioxide media. A common mechanism was observed for all the reaction media under the influence of hydrothermal factors: the kerogen content in the rocks decreases and the yield of free hydrocarbons extractable from the rocks by organic solvents increases. The saturated hydrocarbon content is higher in the group composition of the experiment products compared to the original extract due to decrease in resin and aromatic hydrocarbon content. In the original extract from the Domanikovian rock, as well as in the experiment products, there are two solid dispersed phases, namely, asphaltenes soluble in aromatic solvents and their modified structures of the type of carbenes and carboids insoluble in toluene due to their more condensed structure with a smaller number of aliphatic substituents. The most pronounced decrease in resin content is observed in carbon dioxide medium with a marked increase in asphaltene content in the experiment products relative to the original extract. In hydrogen medium, on the other hand, asphaltene content decreases in the experiment products, but, in comparison with the carbon dioxide medium, carbenes and carboids are formed more intensely due to decomposition of the kerogen structure. Asphaltenes and carbenes-carboids were found to differ in structure and paramagnetic properties.

The primary recovery of some heavy-oil reservoirs can reach relatively high values by using solution-gas-drive technology in which gas dissolved in heavy oil is released and drives the oil when the formation pressure drops below the bubble point. Rheological properties of foamy oil in porous media were studied using conditions of the Orinoco heavy-oil belt in Venezuela as examples. The relative mobilities of foamy and normal oil were compared in core flooding experiments. Improvement of the oil phase as a result of forming the foam structure was analyzed. The research results could be useful for understanding the mobility parameters of heavy oil and increasing the recovery efficiency in heavy-oil reservoirs.

In this paper, based on the principle of superposition of acting forces, we propose a mathematical model for injected fluid-induced stress and calculate the stress distribution and SRV width vs. the stress difference in the formation. The results show that the nature of the propagation of the fracture network in multi-staged hydraulic fracturing depends on the stress in the initial cycle. The larger the horizontal stress difference, the larger the width of the fracture network in the rock. If the stress difference is greater than 5 MPa, the width of the fracture network decreases dramatically. When the net pressure is greater than 8 MPa, the width slowly increases. The calculation results are in good agreement with microseismic monitoring data for conditions in the Southwest shale field (China), suggesting that the proposed model is sufficiently reliable and accurate.

Development of off-shore oilfields presents a number of difficulties and problems during drilling. In this paper, we have tried to describe drillability factors based on a fractal model and calculation of fractal dimensions for rock debris formed by crushing stratigraphic rock. The calculated drillability parameters and the dimensions of rock cuttings showed good correlation with experimental data (correlation coefficient greater than 0.9). Based on the proposed model, we made real-time measurements of the drillability factors. As shown by the results, application of fractal theory to analysis of formation drillability factors lets us more fully take into account the rock features to calculate accurate characteristics of the process.

Improved technology is proposed for the preparation of liquids for hydraulic fracturing (HF)by replacing the liquid cross linker of aqueous polysaccharide gels with solid. The solid cross linker is designed to reduce the logistical costs on transportation and storage of chemical reagents and simplify the technological usage of the HF process. The use of “on the fly” technology leads to more complete and quality gel hydration and its subsequent cross linking. Prolonging the action of the solid cross-linking compositions and also increasing the flowability of the reagent can be achieved as a result of granulation of the reagent and, consequently, the presence of a stage with slow dissolution of the cross linker granules in an aqueous polysaccharide gel.

Heavy ends obtained from thermomechanical distillation of water-tar emulsions of liquid pyrolysis products from a broad fraction of light hydrocarbons and the ethane fraction were studied. Their physicochemical parameters were determined. Various processing schemes for heavy ends were proposed. It was found that the properties of used diesel fuel (UDF) were closest to those of the products. The high densities of the products limited the use of heavy ends as UDF. This problem was solved by proposing a shift of the UDF and vat residue ratio to 4:1 to produce commercial UDF blends.

During the execution of technological operations such as multiple pressure relief or foam separation during well injection, a gas column can form at the wellhead in the annular space, leading to annular pressure buildup (APB). Based on the theory of heat transfer, a model was proposed for calculating the wellbore heat transfer during production. Taking into account the expansion and compression of the fluid, changes in the wellhead volume, the thermodynamic characteristics of the liquid, and the equation of state of the gas, APB calculations were performed. Based on these parameters, the influence of the gas column height on APB was evaluated. The results of the studies show that the coefficients of expansion and compressibility in the annulus depend on density, pressure and temperature: the higher the productivity of the gas well, the higher the temperature and pressure in the annulus; the greater the height of the gas column, the lower the pressure at the wellhead. For a well with a productivity of 30· 10⁴ m³/day and gas column height of 70 m in the annulus, the APB is reduced to atmospheric pressure. Studies of the model for calculating APB of the annular trapped gas provide a theoretical basis for developing optimal technological parameters for the operation of gas wells.